Charging method and charging apparatus

The present invention contains subject matter related to Japanese Patent Application JP 2007-293559 filed in the Japanese Patent Office on Nov. 12, 2007, the entire contents of which being incorporated herein by reference.

1. Field of the Invention

The present invention relates to a charging method and a charging apparatus which make it possible to achieve improved charging efficiency when charging a plurality of batteries consecutively.

2. Description of the Related Art

FIG. 7 is a characteristic diagram showing changes in a charge current which occur when a battery pack including lithium ion batteries having a nominal capacity of 1000 mAh is charged with a current of 1 A. As apparent from the characteristic diagram, the charge current of 1 A flows into the battery pack for a period less than 30 minutes after charging is started. The charge current gradually decreases beyond the 30 minutes after the beginning of charging and reaches 0.2 A when 90 minutes pass after the beginning of charging. When charging is further continued until 150 minutes pass after the beginning of charging, the charge current decreases to about 0.05 A, and the battery pack is substantially fully charged.

FIG. 8 is a characteristic diagram showing charged capacity characteristics of the same battery pack. As apparent from the characteristic diagram, when 150 minutes pass after the beginning of charging to fully charge the battery pack, a charged capacity in the excess of 1000 mAh is obtained. When 90 minutes pass after the beginning of charging, a charged capacity near 1000 mAh is obtained, although the nominal capacity is not reached.

FIG. 9 is a characteristic diagram showing charge capacity percentage characteristics of the same battery pack. The charge capacity percentage characteristics indicate changes in charged capacity occurring after charging is started on an assumption that 100% charged capacity is obtained when 150 minutes pass after the beginning of charging or when the battery pack is fully charged. As apparent from the characteristic diagram, 90 percent of the charge capacity is obtained when 90 minutes pass after charging is started. The diagram also indicates that the 100% charge capacity is obtained when 150 minutes pass after charging is started.

Some charging apparatus for charging secondary batteries including lithium ion batteries as thus described are designed to work with a secondary battery having capacity display means provided on a surface of the battery housing. Specifically, capacity display means is detected by detection means provided at a charging apparatus, and a charge current control circuit is controlled according to output of detection to select an optimal charge current (see JP-A-5-174876 (Patent Document 1)).

According to charging methods and apparatus in the related art, battery packs are charged until 100% charge capacity is reached regardless of the number of the battery packs to be charged. Therefore, in the case of a charging apparatus having only one charging circuit, when there is a plurality of battery packs to be charged, the battery packs are sequentially charged one after another until the 100% charge capacity is obtained. As a result, charging can take a long time depending on the number of battery packs, and a problem therefore arises in that a user may have to wait for such a long time.

Under the circumstance described above, it is desirable to provide a charging method and a charging apparatus which make it possible to achieve improved charging efficiency in charging a plurality of batteries.

According to an embodiment of the invention, there is provided a charging apparatus charging a plurality of batteries having at least two modes including a first mode and a second mode, in which amounts of electricity to charge the batteries are set with reference to a fully charged capacity of the batteries. The apparatus includes mode selection means for selecting either of the first mode and the second mode. The first mode is a mode in which the batteries are charged until the batteries reach a fully charged state. The second mode is a mode in which the charging of the batteries is stopped before the batteries reach the fully charged state.

According to the embodiment of the invention, there is provided a charging method for charging a plurality of batteries, including the steps of setting amounts of electricity to charge the batteries with reference to a fully charged capacity of the batteries to provide a first mode in which the batteries are charged until the batteries reach a fully charged state and a second mode in which the charging of the batteries is stopped before the batteries reach the fully charged state, and charging the plurality of batteries according to a result of selection made by mode selection means for selecting and enabling either of the first mode and second mode.

The charging method and charging apparatus according to the embodiment of the invention as thus described make it possible to achieve improved charging efficiency in charging a plurality of batteries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a charging apparatus utilizing a charging method according to a first embodiment of the invention;

FIG. 2 is a flow chart showing operations of the charging apparatus employing the charging method according to the first embodiment of the invention;

FIG. 3 is a characteristic diagram showing charge current characteristics of a battery pack mounted in a battery slot A and a battery pack mounted in a battery slot B, observed when a 100% charging mode is selected in the first embodiment of the invention;

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Charging system, charging control program, and portable terminal
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Power saving charger
Industry Class:
Electricity: battery or capacitor charging or discharging

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